1. Field of the Invention:
The present invention relates to novel biodegradable "builder" or "cobuilder" preformulations for detergent compositions based on a polyimide and silicate admixture.
By the terms "builder" or "cobuilder" are intended any constituent which improves or enhances the performance of the surfactants in a detergent composition.
2. Description of the Prior Art:
In general, it is known to this art that a detergent "builder" or "cobuilder" serves many functions in a washing or wash liquor. Notably, it can:
(1) effect the removal of undesirable ions, in particular alkaline earth metal (calcium, magnesium) ions by sequestration or precipitation, to prevent the precipitation of anionic surfactants,
(2) provide a reserve of alkalinity and of ionic strength,
(3) maintain extracted soiling materials in suspension,
(4) prevent mineral encrustations onto the laundry during washing.
The tripolyphosphates have long been the builders most typically incorporated into detergent compositions and washing products. However, these are partially responsible for the eutrophication of lakes and slow flowing water when they are not adequately removed by water purification facilities; efforts are thus being made to replace them partially or completely.
Zeolites alone cannot replace the tripolyphosphates; their action has to be reinforced by other additives.
Copolymers of acrylic acid and maleic anhydride (or their alkali metal or ammonium salts) have been described (EP-25,551) as detersive encrustation inhibitors. They present, however, the drawback of not being biodegradable in a natural environment.
To respond to biodegradability requirements, it has been proposed to employ, as a "builder" or "cobuilder" agent for detergent compositions, a range of compounds, peptide polymers, and more precisely amino acid polymers or copolymers.
In particular, sodium polyaspartates and polyglutamates, advantageous by reason of their high biodegradability, display good builder or cobuilder activity (U.S. Pat. No. 4,428,749). It has been demonstrated that it is the negatively charged form of these compounds which is the active species in the detergent formulation.
However, the incorporation of these compounds in their native form in detergent compositions does not prove to be satisfactory. After prolonged storage, the compounds suffer chemical attack on contact with the other constituents of the washing formulation, such as oxidizing and basic agents, ultimately resulting in their degradation.
More recently, it has been proposed to use a precursor of this type of "builder" agent, namely, their polycondensation product (EP-511,037). In contrast to the acid derivatives, polyimides have the advantage of being stable in detergent formulations for prolonged periods of time.
Unfortunately, these compounds are not completely satisfactory at an ecological level, since they are not themselves biodegradable as such. In a detergent medium, namely, in an aqueous alkaline medium, they are converted into a biodegradable species, but, in neutral medium, they remain in a water-insoluble and thus non-biodegradable form.